Colloidal Crystal Template Research Articles

Ordered Hierarchical Porous Structure of PtSn/3DOMM-Al2O3 Catalyst for Promoting Propane Non-Oxidative Dehydrogenation.

Herein, the hierarchical porous catalyst of 3-dimensional ordered macro-mesoporous (3DOMM) Al2O3 supported active PtSn nanoparticles (NPs) was prepared by the combined synthesized path of evaporation-induced self-assembly with colloid crystal template (EISA-CCT) methods. The hierarchical macro-mesoporous composite structure can markedly increase the specific surface area, accommodate the diffusion of propene, and decrease the number of surface acid sites. In addition, the special surface property and pore structure of 3DOMM-Al2O3 can modify the interaction between metals and substrates, as well as stabilize the metal nanoparticle, which promotes the formation of a highly active and stable PtSn phase. The PtSn/3DOMM-Al2O3 catalyst exhibits higher productivity and stability than PtSn/Al2O3 catalysts with macropore and mesopore structures. The PtSn/3DOMM-Al2O3 catalyst displays the best catalytic performance with propylene selectivity over 95% at a propane conversion of 33.9%. The study of the ordered hierarchical porous structure of PtSn/3DOMM-Al2O3 catalysts can contribute to obtaining improved catalysts in industrial processes.

Three-dimensionally ordered macroporous (3DOM) structure promoted the activity and H2O poisoning resistance of CeMn/3DOM-TiO2 catalyst in NH3-SCR

NH3-SCR is an effective mean of NOx removal in the non-electric industry, however, the high activation temperature and poor H2O resistance of SCR catalysts posed a barrier to its application. In this work, a series of three-dimensionally ordered macroporous (3DOM) catalysts were synthesized via a colloidal crystal template (CCT) method, and various characterizations were carried out to explore the physicochemical property of catalysts. The experiment results reveal that Ce0.2Mn0.2/3DOM-TiO2 catalyst presents the excellent low-temperature catalytic activity of nearly 100% at 100 °C. Furthermore, the enhanced H2O resistance is achieved, certified by the unaffected NO remove at 150 °C in the participation of 15 vol% H2O. The characterizations results exhibit that the improved dispersion of the active component and enhanced redox ability are conducive to the low-temperature catalytic activity. N2 adsorption and desorption experiments indicate that catalyst with 3DOM support possesses a larger pore diameter and specific surface area, which may weaken the condensation of H2O in the microporosity of catalysts and improved the H2O resistance of the catalyst. In situ DRIFTS results manifest that Ce0.2Mn0.2/3DOM-TiO2 catalyst could not only absorb more NH3 and generate more surface-active sites, but inhibit the competitive adsorption between H2O and SCR reactants.

Achieving Functionality and Multifunctionality through Bulk and Interfacial Structuring of Colloidal-Crystal-Templated Materials.

Over the past 25 years, the field of colloidal crystal templating of inverse opal or three-dimensionally ordered macroporous (3DOM) structures has made tremendous progress. The degree of structural control over multiple length scales, understanding of mechanical properties, and complexity of systems in which 3DOM materials are a component have increased substantially. In addition, we are now seeing applications of 3DOM materials that make use of multiple features of their architecture at the same time. This Feature Article focuses on the different properties of 3DOM materials that provide functionality, including a relatively large surface area, the interconnectedness of the pores and the resulting good accessibility of the internal surface, the nanostructured features of the walls, the structural hierarchy and periodicity, well-defined surface roughness, and relative mechanical robustness at low density. It provides representative examples that illustrate the properties of interest related to applications including energy storage and conversion systems, sensors, catalysts, sorbents, photonics, actuators, and biomedical materials or devices.

Shape-Preserving Transformation of Electrodeposited Macroporous Microparticles for Single-Particle SERS Applications

Microparticles composed of bicontinuous and ordered macropores are important in many applications. However, rational integration of ordered macropores into a single crystalline microparticle remains a challenge. Here, we report a method to prepare three-dimensionally ordered macroporous (3DOM) Ag7O8NO3 micropyramids via selectively cementing the colloidal crystal templates via an electrochemical method and their shape-preserving transformation into 3DOM Ag micropryamids formed by Ag nanoparticles via a chemical reduction process. The interconnected macropores facilitated the transportation and enrichment of the analyte molecules into the 3DOM Ag micropyramids. The dense Ag nanoparticles on the skeletons of the 3DOM Ag micropyramids provided strong electromagnetic fields. Taken together, a 3DOM Ag micropyramid as a kind of single-particle surface-enhanced Raman scattering (SERS) sensing substrate demonstrated high SERS sensitivity and outstanding SERS signal reproducibility. We explored the application of 3DOM Ag micropyramids in SERS detection of biomolecules (e.g., adenosine, adenine, hemoglobin bovine, and lysozyme) and proved their potentials in distinguishing exosomes from tumor and non-tumor cells. The method can be extended to prepared 3DOM structures of other materials with promising applications in sensing, separation, and catalytic fields.

Ordered Macro-Microporous Single Crystals of Covalent Organic Frameworks with Efficient Sorption of Iodine.

Fashioning microporous covalent organic frameworks (COFs) into single crystals with ordered macropores allows for an effective reduction of the mass transfer resistance and the maximum preservation of their intrinsic properties but remains unexplored. Here, we report the first synthesis of three-dimensional (3D) ordered macroporous single crystals of the imine-linked 3D microporous COFs (COF-300 and COF-303) via a template-assisted modulated strategy. In this strategy, COFs crystallized within the sacrificial colloidal crystal template, assembled from monodisperse polystyrene microspheres, and underwent an aniline-modulated amorphous-to-crystalline transformation to form large single crystals with 3D interconnected macropores. The effects of the introduced macroporous structure on the sorption performances of COF-300 single crystals were further probed by iodine. Our results indicate that iodine adsorption occurred in micropores of COF-300 but not in the introduced macropores. Accordingly, the iodine adsorption capacity of COF single crystals was governed by their micropore accessibility. The relatively long diffusion path in the non-macroporous COF-300 single crystals resulted in a limited micropore accessibility (48.4%) and thus a low capacity in iodine adsorption (1.48 g·g-1). The introduction of 3D ordered macropores can greatly shorten the microporous diffusion path in COF-300 single crystals and thus render all their micropores fully accessible in iodine adsorption with a capacity (3.15 g·g-1) that coincides well with the theoretical one.

Novel preparation method, catalytic performance and reaction mechanisms of PrxMn1−xOδ/3DOM ZSM-5 catalysts for the simultaneous removal of soot and NOx

Three dimensionally-ordered macroporous (3DOM) ZSM-5 zeolite catalysts with hierarchical pore structures have obvious advantages for the catalytic reaction systems containing reactants with different sizes. However, due to the stringent preparation conditions and confined crystallization space, the successful preparation of 3DOM ZSM-5 remains challenging. Herein, we report a novel method for the preparation of 3DOM ZSM-5 zeolite, termed the steam seed-assisted colloid crystal template (SSAC) method. The SSAC method avoids the growth of ZSM-5 crystals based on the confinement effect of the interstices of the polymethylmethacrylate (PMMA) template. The crystallization temperature of ZSM-5 is lower than the glass transition temperature of PMMA, which facilitates the formation of the 3DOM structure. Using 3DOM ZSM-5 as a support, a series of PrxMn1-xOδ/3DOM ZSM-5 catalysts were prepared via incipient wetness impregnation. These catalysts exhibited good catalytic performance for the simultaneous removal of soot and NOx, which can be attributed to the unique hierarchical pore structure, excellent redox properties, the sufficient active oxygen species and appropriate acid sites of overall catalysts. Among the synthesized catalysts, Pr0.2Mn0.8Oδ/3DOM ZSM-5 achieved the highest catalytic activity with a low soot combustion temperature of 417 °C and a wide temperature window of 128 °C-288 °C at 90% NO conversion. Finally, we proposed reaction mechanisms for the catalysts under different temperatures based on the in situ characterization results, kinetic measurements and DFT calculations.

Effects of different B-site ions on the catalytic performance of 3DOM LaBO3 for the simultaneous elimination of NOx and soot particulates from diesel engines

Compared with gasoline engines, diesel engines play an irreplaceable role, but we must also pay attention to the adverse effects of exhaust emissions. The simultaneous elimination NOx and soot particles is an effective way of diesel exhaust abatement. The preparation of catalyst is the core of simultaneous elimination reaction. In this work, three-dimensionally ordered macroporous (3DOM) LaBO3 perovskite catalysts were successfully prepared by colloidal crystal templates method. The as-prepared catalysts were characterized by XRD, SEM, N2 adsorption–desorption, XPS, H2-TPR, NH3-TPD, NO-TPD and NO-TPO. We compared the effects of different B site ions on the catalytic activity through the above characterization methods and 3DOM LaMnO3 shows the best performance with the lowest CO2 peak temperature and the highest NO conversion. The reasons of high performance for desoot are associated with the amount of peroxide species, and de-NOx related to surface acidity and high valence ions.

Novel porous perovskite composite CeO2@LaMnO3/3DOM SiO2 as an effective catalyst for activation of PMS toward oxidation of urotropine

• Novel composite perovskite was successfully prepared. • The novel catalyst has high PMS activation and URO removal efficiency. • The three components in it showed a synergetic effect. Perovskites with stable crystal structure and excellent catalytic performance have attracted extensive attention in peroxomonosulfate (PMS) activation, however, severe agglomeration has always been the main obstacle limiting the catalytic activity of them, so novel perovskite catalysts are urgently needed. In this study, three-dimensional ordered macroporous silica (3DOM SiO 2 ) was prepared by colloidal crystal template method, then CeO 2 @LaMnO 3 /3DOM SiO 2 was prepared by sol-gel method combined with impregnation method and used to activate PMS for urotropine (URO) degradation. CeO 2 @LaMnO 3 /3DOM SiO 2 activated PMS system exhibited high URO removal efficiency and quick kinetic, as 99.98 % URO was degraded even within 30 min. The catalyst has a wide pH range and still has high catalytic activity in the presence of organic matter and inorganic ions. The three components in CeO 2 @LaMnO 3 /3DOM SiO 2 showed a synergetic effect. CeO 2 and LaMnO 3 were uniformly loaded on 3DOM SiO 2 , which effectively avoided agglomeration. The specific surface area of CeO 2 @LaMnO 3 /3DOM SiO 2 was 11.88 times that of LaMnO 3 prepared by sol-gel method. There are two redox cycles of Ce 3+ /Ce 4+ and Mn 2+ /Mn 3+ /Mn 4+ in CeO 2 and LaMnO 3 , respectively, which synergistically realize the activation of PMS. Both quenching experiments and electron paramagnetic resonance (EPR) analysis revealed that that SO 4 − , OH and 1 O 2 jointly achieved the degradation of URO. In summary, CeO 2 @LaMnO 3 /3DOM SiO 2 would be a promising candidate for practical wastewater treatment.

Self-Propelled Structural Color Cylindrical Micromotors for Heavy Metal Ions Adsorption and Screening.

Water contamination resulting from heavy metal ions (HMIs) poses a severe threat to public health and the ecosystem. Attempts are tending to develop functional materials to realize efficient and intelligent adsorption of HMIs. Herein, self-propelled structural color cylindrical micromotors (SCCMs) with reversible HMIs adsorption capacity and self-reporting property are presented. The SCCMs are fabricated by using platinum nanoparticles (Pt NPs) tagged responsive hydrogel of carboxymethyl chitosan (CMC) and polyacrylamide (PAM) to asymmetrically replicate tubular colloidal crystal templates (TCCTs). Owing to the self-propelled motion of the SCCMs, the enhancive ion-motor interactions bring significantly improved decontamination efficiency. Moreover, it is demonstrated that the SCCMs can realize quick and naked-eye-visible self-reporting during the adsorption/desorption process based on their responsive structure color variation and superior adsorption capacity. Thus, it is anticipated that such intelligent SCCMs can significantly facilitate the evolution of sensing assays and diverse environmental fields.

Lead-Free Copper-Based Perovskite Nanonets for Deep Ultraviolet Photodetectors with High Stability and Better Performance.

Considering practical application and commercialization, the research of non-toxic and stable halide perovskite and its application in the field of photoelectric detection have received great attention. However, there are relatively few studies on deep ultraviolet photodetectors, and the perovskite films prepared by traditional spin-coating method have disadvantages such as uneven grain size and irregular agglomeration, which limit their device performance. Herein, uniform and ordered Cs3Cu2I5 nanonet arrays are fabricated based on monolayer colloidal crystal (MCC) templates prepared with 1 μm polystyrene (PS) spheres, which enhance light-harvesting ability. Furthermore, the performance of the lateral photodetector (PD) is significantly enhanced when using Cs3Cu2I5 nanonet compared to the pure Cs3Cu2I5 film. Under deep ultraviolet light, the Cs3Cu2I5 nanonet PD exhibits a high light responsivity of 1.66 AW−1 and a high detection up to 2.48 × 1012 Jones. Meanwhile, the unencapsulated PD has almost no response to light above 330 nm and shows remarkable stability. The above results prove that Cs3Cu2I5 nanonet can be a great potential light-absorbing layer for solar-blind deep ultraviolet PD, which can be used as light absorption layer of UV solar cell.

Non-gelated polymeric photonic crystal films

A rapid curing method for the preparation of colloidal photonic crystal films is presented. Firstly, a colloidal crystal array template was prepared by self-assembly of nanospheres, and then a dilute polymer solution was poured into the gap of the template. Then the composite photonic film was obtained as the polymer solution was cured. Such films have good properties in mechanical strength, anti pH interference, rapid solvent response and are easy to preserve. The films show good linear response to ethanol aqueous solutions of different concentrations, and the response equilibrium takes less than 20 s. The films also show long-term stability and reusability, and further functionalization can make the films multi-sensitive.

A novel three-dimensionally ordered macroporous aerogel for capturing radioactive gaseous iodine

To further improve the adsorption capacity of radioiodine in nuclear industry waste gas, the sol-gel combined with colloidal crystal template method was used to successfully introduce a three-dimensionally ordered macroporous (3DOM) structure into the silver-silica aerogel. The effects of the 3DOM structure on the micropore surface area, phase composition, iodine capture capacity and regeneration performance of the aerogels were studied. The results show that the 3DOM structure can effectively increase the micropore surface area of silver-silica aerogel, avoid the agglomeration and grain growth of active components silver, and significantly improve the iodine capture capacity. It will lay the foundation for the application of this new material in the capture of radioactive iodine in the future.

Multifunctional fish gelatin hydrogel inverse opal films for wound healing

BackgroundWound healing has become a worldwide healthcare issue. Attempts in the area focus on developing patches with the capabilities of avoiding wound infection, promoting tissue remolding, and reporting treatment status that are of great value for wound treatment.ResultsIn this paper, we present a novel inverse opal film (IOF) patch based on a photo-crosslinking fish gelatin hydrogel with the desired features for wound healing and dynamic monitoring. The film with vibrant structure colors was constructed by using the mixture of fish gelatin methacryloyl, chitosan, and polyacrylic acid (PAA) to replicate colloidal crystal templates. As the structures of these natural biomolecules are well-retained during the fabrication, the resultant IOF was with brilliant biocompatibility, low immunogenicity, antibacterial property, as well as with the functions of promoting tissue growth and wound healing. In addition, the IOF presented interconnected nanopores and high specific surface areas for vascular endothelial growth factor loading, which could further improve its angiogenesis capability. More attractively, as the pH-responsive PAA was incorporated, the IOF patch could report the wound healing status through its real-time structural colors or reflectance spectra.ConclusionsThese features implied the practical value of the multifunctional fish gelatin hydrogel IOFs in clinical wound management.Graphical

Fabrication and UV photoresponse of ordered ZnO nanonets using monolayer colloidal crystal template

Two-dimensionally Ordered macroporous films have attracted attention for their potential application such as sensors and optoelectronic devices. Here, highly ordered ZnO nanonets film were successfully prepared by a facile method, which uses monolayer colloidal crystal template composed of polystyrene spheres and sol-gel spin-coating method. Furthermore, ZnO nanonets-based ultraviolet photodetector are constructed, which showed high on/off current ratio of 2.7 × 10 5 under 370 nm UV light illumination with an intensity of 0.85 mW/cm 2 .

Effects of calcination rate and temperature on microstructure and gaseous iodine capture capacity of 3DOM-SiO2 aerogels

Three-dimensional ordered macropores silica (3DOM-SiO2) aerogels prepared by the sol-gel and colloidal crystal template technology have attracted wide attention in the field of gaseous radioiodine capture. 3DOM effectively reduces the diffusion resistance of gas, increases the specific surface area and improves the capture capacity of the aerogels. The optimization of the calcination process for removing colloidal crystal templates is very important for the construction of 3DOM. The effects of calcination rate and calcination temperature on the microstructure, specific surface area, surface official energy group, phase composition, and iodine adsorption capacity of 3DOM-SiO2 were systematically investigated. The results showed that the calcination rate and temperature affected the iodine capture capacity of 3DOM-SiO2 by affecting the formation of macropores, mesopores, and micropores and the content of adsorbed water in the pore structure. The optimization of the 3DOM preparation process provides a scientific basis for the capture and application of radioactive iodine.

Highly efficient adsorption of radioiodine by a three-dimensional ordered macroporous bismuth-silica composite aerogel

At present, the iodine adsorbents used in the post-treatment iodine removal system are silver-loaded zeolites (AgZ and AgX), because silver and iodine have higher reactivity. The main advantages of bismuth over silver in iodine capture include high-cost performance, non-toxicity and high adsorption capacity. In this work, the sol–gel method combined with the colloidal crystal template method was used to introduce the three-dimensional ordered macroporous structure into the bismuth-silica aerogels. The detected adsorption capacity reaches 696 ± 21 mg/g, which is approximately 3-fold higher than that of silver-loaded zeolites. And the adsorption mechanism of iodine by the bismuth-silica aerogels was revealed. It is found that the bismuth-silica aerogels have chemical adsorption and physical adsorption for iodine, and BiI3 is mainly formed by the chemical reaction between Bi and I2.

(Digital Presentation) Synthesis of Multisize Layered Silica Inverse Opal Photonic Crystals

Today, human beings have found an increasing need for energy. The ever-increasing effort to shrink information systems at higher speeds has led to the common idea that photons are used as carriers of information instead of electrons. Photonic crystals have a structure whose dielectric constants and refractive indices change alternately in one, two, or three dimensions, which are called one-dimensional, two-dimensional, and three-dimensional photon crystals. Periodicity in the refractive index of the crystal structure causes a photonic bandgap that includes a range of frequencies in which light with a frequency of this range is not allowed to pass the crystal structure and is reflected or absorbed.In this work, Poly(methyl methacrylate) (PMMA) microspheres of different sizes were first synthesized using the suspension polymerization method. Concentrations of used materials including initializer, monomer, reaction temperature, reaction time, and rotation speed play important roles in determining the final diameter of PMMA microspheres. Then, the vertical deposition method is used for the growth of multi-layered opals of different sizes, one on top of another. On the other hand, inverse opals have porous and organized structures that are made using opals as the template. The method used in this study to make multisize layered inverse opal made of silica is as follows: 1- Fabrication of a uniform layer of polymer microspheres on a glass substrate with a specified size as a colloidal crystal template 2- Infiltration of void space between the microspheres of the opal template 3- Creating the next layer with different size on the first layer 4- Reinjection of the silica precursor. 5- Repeating the coating layer and injection of the precursor. 6- Finally, selective removal of the opal template by calcination or etching with an organic solvent to create the porous structure of the multisize layered Silica inverse opal photonic crystals. The silica precursor contains a mixture of ethanol, TEOS tetraethyl orthosilicate, and hydrochloric acid.The results show that the fabricated inverse opals are organized, crack-free, and uniform. It is possible to make the desired number of layers by changing the concentration of the PMMA microspheres' colloidal suspension. By changing the characteristics of photonic crystals, such as their constituent materials and refractive indices, lattice constants, and the number of layers, it is possible to control their photonic properties which are beneficial for different applications.

Evaluation of three-dimensionally ordered macroporous LaFe1−xCoxO3 perovskites and their performance for catalytic oxidation of methane

Nowadays, excess methane emissions have caused serious environmental problems, of which catalytic oxidation is a practical and economically feasible technique for its decomposition and harm reduction. Here, three‐dimensionally ordered macroporous (3DOM) LaFe1−xCoxO3 (x = 0, 0.1, 0.3, 0.5) were prepared by colloidal crystal template (CCT) method using polynomial methacrylate (PMMA) as templates in order to evaluate their catalytic activities for methane. Numerous analytical techniques were used to characterize the physicochemical properties of as-prepared perovskite catalysts. The results showed that the morphology of the catalysts depended strongly on the PMMA template and an appropriate calcination temperature was decisive for the formation of a high-quality 3DOM structure, which affected the textural parameters, the surface compositions of the catalysts and further determined their catalytic activities for methane. Along with the doping of Co for Fe at the B site, the BET surface areas and crystallite sizes could be optimized, and the ratios of Fe4+/Fe3+, absorbed oxygen (Oads)/lattice oxygen (Olat) both increased with the increment of Co substitution, which were beneficial to improve the catalytic activity on CH4. However, the surface carbonate or hydroxide compounds also increased with the increment of Co doping and did harm to the catalytic activity in an opposite way. The final result was that the 3DOM LaFeO3 calcined at 700 ℃ (Ea = 70.9 kJ/mol, T50% = 548 ℃, T90% = 652 ℃), with the optimal pore size, pore volume, Fe4+/Fe3+ ratio, H2-TPR reducibility, on stream testing stability and carbon deposition resistance in low temperature, showed much better performance than the Co-doped 3DOM LaFe1−xCoxO3 (x = 0.1, 0.3, 0.5) in the methane catalytic process. However, it was also predictable that the performance of methane oxidation by Co-doped perovskites can be improved if the surface carbonate or hydroxide compounds can be effectively controlled in the future by surface engineering methods like acid treated or others to eliminate La segregation on its surface.

Preparation of 3DOM ZrTiO4 Support, WxCeMnOδ/3DOM ZrTiO4 Catalysts, and Their Catalytic Performance for the Simultaneous Removal of Soot and NOx.

As an efficient and durable engine, a diesel engine has a broad application. However, soot particles (PM) and nitrogen oxides (NOx) coming from diesel engines are the main causes of air pollution, so it is necessary to design and prepare an effective catalyst for the simultaneous elimination of PM and NOx. In this work, a novel 3DOM ZrTiO4 support and a series of WxCeMnOδ/3DOM ZrTiO4 catalysts (where x indicates the wt% of W) were designed and fabricated by the colloidal crystal template technique. Among the as-prepared catalysts, the W1CeMnOδ/3DOM ZrTiO4 catalyst exhibits the highest NO conversion rate (52%) at the temperature of maximum CO2 concentration (474°C) and achieves 90% NO conversion in the temperature range of 250–396°C. The excellent catalytic performance is associated with the macroporous structure, abundant oxygen vacancies, sufficient acid sites, and the synergistic effect among the active components. The possible reaction mechanisms of WxCeMnOδ/3DOM ZrTiO4 catalysts were also discussed based on the characterization results.

Screen-Printed Carbon Electrodes with Macroporous Copper Film for Enhanced Amperometric Sensing of Saccharides.

A porous layer of copper was formed on the surface of screen-printed carbon electrodes via the colloidal crystal templating technique. An aqueous suspension of monodisperse polystyrene spheres of 500 nm particle diameter was drop-casted on the carbon tracks printed on the substrate made of alumina ceramic. After evaporation, the electrode was carefully dipped in copper plating solution for a certain time to achieve a sufficient penetration of solution within the polystyrene spheres. The metal was then electrodeposited galvanostatically over the self-assembled colloidal crystal. Finally, the polystyrene template was dissolved in toluene to expose the porous structure of copper deposit. The morphology of porous structures was investigated using scanning electron microscopy. Electroanalytical properties of porous copper film electrodes were evaluated in amperometric detection of selected saccharides, namely glucose, fructose, sucrose, and galactose. Using hydrodynamic amperometry in stirred alkaline solution, a current response at +0.6 V vs. Ag/AgCl was recorded after addition of the selected saccharide. These saccharides could be quantified in two linear ranges (0.2–1.0 μmol L−1 and 4.0–100 μmol L−1) with detection limits of 0.1 μmol L−1 glucose, 0.03 μmol L−1 fructose, and 0.05 μmol L−1 sucrose or galactose. In addition, analytical performance of porous copper electrodes was ascertained and compared to that of copper film screen-printed carbon electrodes, prepared ex-situ by the galvanostatic deposition of metal in the plating solution. After calculating the current densities with respect to the geometric area of working electrodes, the porous electrodes exhibited much higher sensitivity to changes in concentration of analytes, presumably due to the larger surface of the porous copper deposit. In the future, they could be incorporated in detectors of flow injection systems due to their long-term mechanical stability.